Area Forecast Discussion
Issued by NWS Central Illinois

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FXUS63 KILX 131105
AFDILX

AREA FORECAST DISCUSSION
National Weather Service Lincoln IL
505 AM CST SAT FEB 13 2016

.SHORT TERM...(Today)
ISSUED AT 323 AM CST SAT FEB 13 2016

1043mb high centered over the eastern Dakotas will build
southeastward today, providing cold and dry weather across central
Illinois.  Skies will be sunny to start the day: however, mid/high
clouds ahead of the next approaching system will begin increasing
from the west as the day progresses.  After very cold early morning
lows in the single digits, afternoon high temperatures will climb
into the teens.

.LONG TERM...(Tonight through Friday)
ISSUED AT 323 AM CST SAT FEB 13 2016

Short-wave trough evident on 09z/3am water vapor imagery over the
Pacific Northwest will track across the Northern Rockies today, then
will dig southeastward into the region on Sunday.  Light to moderate
snow will develop in advance of this feature across Iowa into
northern Missouri this evening, then will spread eastward into the
KILX CWA overnight.  Airmass will initially be quite dry, so even
after the arrival of mid/upper lift, it will take several hours
before the profile moistens sufficiently to support snow reaching
the ground.  Based on time-height cross-sections, it appears profile
saturation will occur along/northwest of the I-55 corridor between
06z and 09z...then further east to the Indiana border toward 12z.
Isentropic lift will be fairly robust, with 30-40kt of upglide noted
on the 295K surface coincident with low condensation deficits and
specific humidity values of 2-3g/kg.  End result will be a prolonged
period of light to moderate snow from late tonight through Sunday
afternoon.  Given expected QPF during that time frame, am
forecasting a general 2-3 inches across all of central and southeast
Illinois.  Slightly higher amounts of 3-4 inches will be focused
across the N/NW CWA...mainly along/north of a Canton to Minonk line.
In addition to the snowfall, brisk southeasterly winds gusting to
20-25mph will create some blowing/drifting snow on Sunday.  Due
to anticipated travel inconveniences during this event, have opted
to issue a Winter Weather Advisory across the entire area from 09z
Sun through 00z Mon.  Once the initial upper wave passes to the
east, synoptic lift will quickly diminish late Sunday
afternoon/evening.  As a result, am expecting the snow to taper
off and come to an end Sunday night with no additional
accumulation.

Cool/dry weather will be on tap for Monday, before yet another
system comes into the picture Monday night into Tuesday.  Will have
to keep a close eye on thermal profiles as the time approaches, as
enough warming may occur to present some precip type issues.  In
particular, if the elevated warm layer can become pronounced enough
over the cold/snow-covered ground, a period of freezing rain could
be possible late Monday night into early Tuesday morning before
surface temps rise above freezing.  At this point, will maintain
snow early in the event, transitioning to either a rain/snow mix or
all rain by Tuesday afternoon.

After that, the main story further out in the extended will be a
marked warming trend by the end of next week.  All models are
showing a pronounced upper-level ridge building across the Midwest
resulting in temperatures soaring into the 50s by Friday.

&&

.AVIATION...(For the 12Z TAFS through 12Z Sunday morning)
ISSUED AT 502 AM CST SAT FEB 13 2016

VFR conditions are expected over the entire area through 06z
before snow and IFR cigs develop from west to east during the
remainder of the forecast period. Cold high pressure will
push across the area today bringing quiet weather to the
TAF area. Other than some cirrus streaming across the region
today, no aviation concerns are expected until after midnight
tonight as another storm system approaches the area. We look
for snow to develop in the 06z to 09z time frame at PIA and
SPI and by 12z over at CMI. Once the snow moves in, MVFR to
IFR cigs and vsbys will develop by dawn over the entire area.
Surface winds today will be mostly out of a northerly direction
at 10 mph or less, and then switch into the east to southeast
late tonight with speeds increasing to between 10 and 15 kts
by Sunday morning.

&&

.ILX Watches/Warnings/Advisories...
Winter Weather Advisory from 3 AM to 6 PM CST Sunday for
ILZ027>031-036>038-040>057-061>063-066>068-071>073.

&&

$$

SHORT TERM...Barnes
LONG TERM...Barnes
AVIATION...Smith



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